Everything you need to know about: the Boeing AH-64 Apache

The AH-64 Apache is a purpose-built two-seat, twin-turboshaft, all-weather, night capable attack helicopter primarily operated by the US Army. Originally designed by Hughes Helicopters in 1975, to replace the aging AH-1S, through a series of mergers it is now produced and exported by Boeing. The AH-64 first entered service in 1986 as the AH-64, and still serves as the primary attack helicopter for the US Army as the AH-64D, pictured above.
Technical Specifications:
Crew: 2, one pilot, one WSO/co-pilot
Maximum Speed: 158 knots, DNE speed 197 knots
Rate of Climb: up to 2,000 ft/min under ideal conditions, up to a service ceiling of 21,000 ft
Powerplant: 2 General Electric T700-GE-701C Turboshaft engines, each with a shaft horsepower of 1,890
Armament:
One undercarriage mounted 30mm M230 chain gun carrying 1,200 rounds of ammunition
Four wing stub pylons, each able to carry:
4 AGM-114 Hellfire laser-guided ATGMs (for a total of 16, though a more common combat load is 8)
19 70mm rockets, typically Hydra 70 unguided air-to-ground rockets
And on the AH-64D, two wingtip pylons each able to carry one AIM-92 Stinger air-to-air missile, for self defence.
Sensors:
Nose-mounted sensor suite containing a FLIR and night-vision systems
Helmet-mounted gun-queuing system allowing the WSO to control the gun with their head
On the AH-64D, the Lockheed Martin / Northrop Grumman AN/APG-78 Longbow fire-control radar, allowing the Apache to track targets up to 260 nm away

Development and design
In 1972, the US Army was looking for an anti-armor attack helicopter to replace the AH-1 Cobra. Forbidden from operating fixed wing aircraft, they wanted a helicopter better than the Cobra in every regard: range, payload, and performance. In November 1972, the Army submitted a request for proposals on their now designated AAH program: Advanced Attack Helicopter.
Bell, Lockheed, Sikorsky, and Boing Vertol/Grumman all submitted proposals, however the Department of Defense selected Bell and Hughes designs, the YAH-63 and YAH-64, respectively, as finalists. The YAH-64 first flew on September 30, 1975, and after seeing Bell's design, the YAH-63, the DoD selected the YAH-64 due to its more damage resistant 4-blade rotor, and more stable conventional landing gear arrangement as opposed to the YAH-63s tricycle arrangement. After its selection, a third prototype was built and the previous two were upgraded to incorporate the third's sensor suite, avionics, weapon control systems, and wing stub pylons.
In 1975 testing of then brand-new AGM-114 Hellfire anti-tank missiles began on the YAH-64, now designated the AH-64A. The A model featured upgraded engines, and was the first model to have the GE turboshaft engines delivering greater power than the engines selected for the prototype. It was christened the 'Apache' in 1981 in keeping with the Army tradition of naming helicopters after Native American tribes (Iroquois, Blackhawk, etc). In 1982, the first production model AH-64A rolled off the Hughes production line and was purchased by the US Army for a flyaway cost of 7M$.
In 1984, Hughes Helicopters was purchased by McDonnell Douglas, who began looking into an upgraded Apache, the AH-64B. The B was to feature upgraded sensors, weapon control systems, and avionics on the same, ultra-capable platform. This was cancelled in 1988, however the idea did not fade. In 1990, the AH-64D Apache Longbow was proposed, with a dome-mounted fire control radar mounted above the rotor. By 1992, the proposal had been approved and prototyping began.
Protoyping for the AH-64D ended in April of 1995, and it was found to be much more effective than the AH-64A. When pitted against a numerically superior unit of AH-64As, the D proved to be 7 times more survivable and 4 times more lethal than its counterpart. In October of that year, full production of the D model was approved, and it entered service in 1997.

Combat/Operational History
The Apache first saw service in the Gulf War. Nearly half of all AH-64s were deployed to Saudi Arabia after Iraq's invasion of Kuwait. During Operation Desert Storm, a total of 277 Apaches were deployed, and scored 278 tank kills, as well as numerous other vehicle kills. Only one Apache was lost, due to a hit from an RPG, however, both of its crew survived. The Apache had proven to be invaluable. But it wasn't without issue. The AH-64 provided unique logistical complications. Maintenance and logistics vehicles were unable to keep up with the Apache's high workload, and even with the unofficial grounding of all remaining Apaches worldwide, AH-64s only flew 1/5 of their planned flight hours.
In the 1990s, the Apache was deployed to Bosnia and Kosovo, however, it encountered some problems. Insufficient training of pilots, and deficiencies in night vision equipment, fuel tanks, and survivability resulted in the grouding of the Balkans fleet in December 2000, following the crash of an Apache in 1999 due to a faulty tail rotor.
US Apaches served during Operation Enduring Freedom in Iraq and Afghanistan from 2001 onwards. They proved capable of providing accurate CAS, and effective even against unarmored targets. The Longbow targeting radar was removed for Operation Iraqi Freedom due to a lack of armored targets. In March 2003, 31 Apaches were damaged and one shot down in a failed attack on an armored brigade. The helicopter came down intact and both crew members were captured. An air strike destroyed the downed helicopter the following day, preventing its capture.

In 2013, the US Army received the first AH-64E Apache Guardians. Es were capable of controlling UAV drones, as well as providing fire control for other units. 24 Apache Guardians were deployed in 2013, and by the end of their tour in 2014, they had proven much more effective than D models. The E model was 20 mph faster, resulting in faster response times, and was more fuel efficient, allowing it to remain on-station for 3-3.5 hours, an upgrade over the previous 2.5 hours. Taliban forces accustomed to seeing AH-64Ds were caught off guard by Apaches attacking sooner and remaining longer than they had previously. Apache Guardian crews made use of its capability to control and receive data from UAVs to find and track targets, as well as using them to gain a higher-altitude perspective of the battlefield, allowing engagement from standoff ranges.
Currently, the Army is implementing a plan to begin phasing out its OH-58 Kiowas and replace them with AH-64Es acquired from Air National Guard units. The Army found that Apache Guardians were more effective than its older Kiowas and a cheaper alternative to a new reconnaissance helicopter. In March 2015, the first joint havy attack/reconnaissance unit was formed, composed of 24 attack Apaches, 24 recon Apaches, as well as 12 UAVs.
In 2014, Apaches were deployed as part of Operation Inherent Resolve, and participated in the Battle of Fallujah, as well as the Battle of Mosul. The Apache also took up night operations in support of Iraqi forces.

The Apache is currently in service with 16 countries, including the US. To date, over 2000 Apaches have been produced, and is continuing to be produced until 2026. The Apache will remain in service until the Army's FVL (Future Vertical Lift) program is completed in 2040, at which time the Apache will be retired.
Well. You made it. The end of my second helicopter post. My first, about the Mil Mi-24 Hind, which can be found here: http://imgur.com/gallery/YdA95 I had a lot of fun putting this post together, and I was going to wait longer but I made the mistake of reading up on it last night and ended up making this earlier than anticipated. I have a feeling you guys won't complain.